¹Michael T. Thorpe,¹A. Deanne Rogers,²Thomas F. Bristow,¹Cong Pan
¹Department of Geosciences, State University of New York at Stony Brook University, Stony Brook, NY, USA
²NASA Ames Research Center, Moffett Field, CA

Thermal emission spectroscopy is used to determine the mineralogy of sandstone and mudstone rocks as part of an investigation of linear spectral mixing between sedimentary constituent phases. With widespread occurrences of sedimentary rocks on the surface of Mars, critical examination of the accuracy associated with quantitative models of mineral abundances derived from thermal emission spectra of sedimentary materials is necessary. Though thermal emission spectroscopy has been previously proven to be a viable technique to obtain quantitative mineralogy from igneous and metamorphic materials, sedimentary rocks, with natural variation of composition, compaction, and grain size, have yet to be examined. In this work, we present an analysis of the thermal emission spectral (~270-1650 cm−1) characteristics of a suite of 13 sandstones and 14 mudstones. X-ray diffraction and traditional point counting procedures were all evaluated in comparison with thermal emission spectroscopy. Results from this work are consistent with previous thermal emission spectroscopy studies and indicate that bulk rock mineral abundances can be estimated within 11.2 % for detrital grains (i.e., quartz and feldspars) and 14.8 % for all other mineral phases present in both sandstones and mudstones, in comparison to common in situ techniques used for determining bulk rock composition. Clay-sized to fine silt-sized grained phase identification is less accurate, with differences from the known ranging from ~5-24% on average. Nevertheless, linear least squares modeling of thermal emission spectra is an advantageous technique for determining abundances of detrital grains and sedimentary matrix, and for providing a rapid classification of clastic rocks.

Reference
Thorpe MT, Rogers AD, Bristow TF, Pan C (2015) Quantitative Compositional Analysis of Sedimentary Materials Using Thermal Emission Spectroscopy: 1. Application to Sedimentary Rocks. Journal of Geophysical Research Planets (in Press)
Link to Article [DOI: 10.1002/2015JE004863]
Published by arrangement with John Wiley & Sons

^1,2,3S. Goderis, ³A.D. Brandon, ⁴B. Mayer, ⁴M. Humayun
¹Earth System Science, Vrije Universiteit Brussel, Brussels, Belgium
²Department of Analytical Chemistry, Ghent University, Ghent, Belgium
³Department of Earth and Atmospheric Sciences, University of Houston, Houston, TX, USA
⁴National High Magnetic Field Laboratory and Department of Earth, Ocean & Atmospheric Science, Florida State University, Tallahassee, FL, USA

Ubiquitous nucleosynthetic isotope anomalies relative to the terrestrial isotopic composition in Mo, Ru, and other elements are known from both bulk chondrites and differentiated meteorites, but Os isotope ratios reported from such meteorites have been found to be indistinguishable from the terrestrial value. The carriers of s- and r-process Os must thus have been homogeneously distributed in the solar nebula. As large Os isotope anomalies are known from acid leachates and residues of primitive chondrites, the constant relative proportions of presolar s- and r-process carriers in such chondrites must have been maintained during nebular processes. It has long been assumed that partial melting of primitive chondrites would homogenize the isotopic heterogeneity carried by presolar grains. Here, ureilites, carbon-rich ultramafic achondrites dominantly composed of olivine and low-Ca pyroxene, are shown to be the first differentiated bulk Solar System materials for which nucleosynthetic Os isotope anomalies have been identified. These anomalies consist of enrichment in s-process Os heterogeneously distributed in different ureilites. Given the observed homogeneity of Os isotopes in all types of primitive chondrites, this Os isotope variability among ureilites must have been caused by selective removal of s-process-poor Os host phases, probably metal, during rapid localized melting on the ureilite parent body. While Mo and Ru isotope anomalies for all meteorites measured so far exhibit s-process deficits relative to the Earth, the opposite holds for the Os isotope anomalies in ureilites reported here. This might indicate that the Earth preferentially accreted olivine-rich restites and inherited a s-process excess relative to smaller meteorite bodies, consistent with Earth’s high Mg/Si ratio and enrichment of s-process nuclides in Mo, Ru, and Nd isotopes. Our new Os isotope results imply that caution must be used when applying nucleosynthetic isotope anomalies as provenance indicators between different classes of meteorites.

Reference
Goderis S, Brandon AD, Mayer B, Humayun M (2015) s-Process Os isotope enrichment in ureilites by planetary processing. Earth and Planetary Science Letters 431, 110–118
Link to Article [doi:10.1016/j.epsl.2015.09.021]
Copyright Elsevier

¹Evelyn Füri, ^2,3Peter H. Barry, ²Lawrence A. Taylor, ¹Bernard Marty
¹Centre de Recherches Pétrographiques et Géochimiques, CNRS-UL, 15 rue Notre Dame des Pauvres, BP 20, 54501 Vandoeuvre-lès-Nancy, France
²Planetary Geosciences Institute, Department of Earth Planetary Sciences, University of Tennessee, Knoxville, TN 37996-1410, USA
³Department of Earth Sciences, University of Oxford, Oxford OX1 3AN, UK

Nitrogen and noble gas (Ne–Ar) abundances and isotope ratios, determined by step-wise CO2 laser-extraction, static-mass spectrometry analysis, are reported for bulk fragments and mineral separates of ten lunar mare basalts (10020, 10057, 12008, 14053, 15555, 70255, 71557, 71576, 74255, 74275), one highland breccia (14321), and one ferroan anorthosite (15414). The mare basalt sub-samples 10057,183 and 71576,12 contain a large amount of solar noble gases, whereas neon and argon in all other samples are purely cosmogenic, as shown by their 21Ne/22Ne ratios of ≈0.85 and 36Ar/38Ar ratios of ≈0.65. The solar-gas-free basalts contain a two-component mixture of cosmogenic 15N and indigenous nitrogen ((<0.5 ppm). Mare basalt 74255 and the olivine fraction of 15555,876 record the smallest proportion of ¹⁵N_cosm; therefore, their δ¹⁵Nδ15N values of −0.2 to +26.7‰+26.7‰ (observed at the low-temperature steps) are thought to well represent the isotopic composition of indigenous lunar nitrogen. However, δ¹⁵Nδ15N values ≤−30‰≤−30‰ are found in several basalts, overlapping with the isotopic signature of Earth’s primordial mantle or an enstatite chondrite-like impactor. While the lowest δ¹⁵Nδ15N values allow for nitrogen trapped in the Moon’s interior to be inherited from the proto-Earth and/or the impactor, the more ¹⁵N-enriched compositions require that carbonaceous chondrites provided nitrogen to the lunar magma ocean prior to the solidification of the crust. Since nitrogen can efficiently be incorporated into mafic minerals (olivine, pyroxene) under oxygen fugacities close to or below the iron-wustite buffer (Li et al., 2013), the mare basalt source region is likely characterized by a high nitrogen storage capacity. In contrast, anorthosite 15414 shows no traces of indigenous nitrogen, suggesting that nitrogen was not efficiently incorporated into the lunar crust during magma ocean Differentiation.

Reference
Füri E, Barry PH, Taylor LA, Marty B (2015) Indigenous nitrogen in the Moon: Constraints from coupled nitrogen–noble gas analyses of mare basalts. Earth and Planetary Science Letters 431, 195–205
Link to Article [doi:10.1016/j.epsl.2015.09.022]
Copyright Elsevier

Paul R. Renne^1,2, Courtney J. Sprain^1,2, Mark A. Richards², Stephen Self², Loÿc Vanderkluysen³, Kanchan Pande^4
11Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, CA 94709, USA.
²Department of Earth and Planetary Science, University of California–Berkeley, Berkeley, CA 94720, USA.
³Department of Biodiversity, Earth and Environmental Science, Drexel University, Philadelphia, PA 19104, USA.
⁴Department of Earth Sciences, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, India.

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Reference
Renne PR, Sprain CJ, Richards MA, Self S, Vanderkluysen L, Pande K (2015) State shift in Deccan volcanism at the Cretaceous-Paleogene boundary, possibly induced by impact. Science 6256:76-78.
Link to Article [doi:10.1126/science.aac7549]

Lujendra Ojha¹, Mary Beth Wilhelm^1,2, Scott L. Murchie³, Alfred S. McEwen⁴, James J. Wray¹, Jennifer Hanley⁵, Marion Massé⁶ & Matt Chojnacki^4
1School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia 30308, USA
²Space Science and Astrobiology Division, NASA Ames Research Center, Moffett Field, California 94035, USA
³Applied Physics Laboratory, Laurel, Maryland 20723, USA
⁴Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona 85721, USA
⁵Department of Space Studies, Southwest Research Institute, Boulder, Colorado 80302, USA
⁶Laboratoire de Planétologie et Géodynamique, Nantes 44322, France

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Reference
Ojha L, Wilhelm MB, Munchie SL, McEwen AS, Wray JJ, Hanley J, Massé M & Chojnacki M (2015) Spectral evidence for hydrated salts in recurring slope lineae on Mars. Nature Geoscience 8 (in press).
Link to Article [doi:10.1038/ngeo2546]

Diane T. Wetzel¹, Erik H. Hauri², Alberto E. Saal¹ & Malcolm J. Rutherford^1
1Department of Geological Sciences, Brown University, Providence, Rhode Island 02912, USA
²Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington DC 20015, USA

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Reference
Wetzel DT, Hauri EH, Saal AE & Rutherford MJ (2015) Carbon content and degassing history of the lunar volcanic glasses. Nature Geoscience 8:755–758.
Link to Article [doi:10.1038/ngeo2511]

Bruno Scaillet
Bruno Scaillet is at Institut des Sciences de la Terre d’Orléans, CNRS/Université d’Orléans/BRGM, 1a Rue de la Férollerie 45071, Orléans, France

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Reference
Scaillet B (2015) Planetary science: Carbon in the Moon. Nature Geoscience 8:747–748.
Link to Article [doi:10.1038/ngeo2530]